The present invention relates to water-in-oil (W/O) emulsions, to compositions for cosmetic, pharmaceutical, hygiene or dermatological use, comprising such an emulsion, as well as to their use in the cosmetic, pharmaceutical, dermatological and/or hygiene fields.
These compositions may constitute care products for the skin, including the scalp, and/or make-up products for the skin, mucous membranes (the inside of the eyelids), semi-mucous membranes (lips), keratin fibres (hair, eyelashes, nails) or alternatively make-up products for the body.
Make-up compositions, in particular foundations, are generally in the form of a more or less fluid cream comprising fatty substances such as oils and a particulate phase generally composed of fillers and pigments.
It is generally sought to introduce into the fatty phase compounds such as silicones, which provide softness and fluidity. However, it is known that as the silicone oil content increases, it is more difficult to obtain a stable W/O emulsion, not only over time but also when it is subjected to large variations in temperature. In fact, the fluidity of the formula can be the cause of phenomena of instability over time, such as the release of oil at the surface, sedimentation of the pigments, thickening, etc.
With the aim of reducing these phenomena, it has been proposed in U.S. Pat. No. 4,698,178 to use a new class of silicone surfactants associated with polyols for the low temperatures, and with electrolytes or with metal soaps for the high temperatures.
The improvement in the stability of W/O emulsions has also been studied in patent application EP 331,833, which describes the use of oxyalkylenated silicones combined with water-swellable inorganic clays, and in patent application EP-A-612,517, which recommends the use of a combination of a silicone containing oxyalkylene groups and pendant alkyls with a gelling and/or thickening agent.
Nevertheless, when these compositions are applied to the skin, mucous membranes or semi-mucous membranes, they have the disadvantage of transferring to another surface. This means that the composition, once applied, is liable to be deposited, at least partly, on certain supports with which it is placed in contact, such as, for example, a glass, an item of clothing or the skin.
Once deposited, the said composition leaves a trace on the said support. This thus results in mediocre staying power of the composition on the skin or the mucous membranes, thus making it necessary to regularly renew its application.
Moreover, the appearance of unacceptable traces of the composition on certain items of clothing, and in particular on shirt collars, can discourage women from using this type of make-up.
Another disadvantage of these compositions lies in the problem of migration. Specifically, it has been found that certain compositions have a tendency to diffuse or migrate inside the fine lines and/or wrinkles on the skin, in the case of foundations; in the fine lines surrounding the lips, in the case of lipsticks; and in the folds of the eyelids, in the case of eyeshadows. The appearance of lines in the make-up, generated by the movements of the eyelids, has also been found, in particular in the case of eyeshadows. All of these phenomena generate a displeasing effect which, needless to say, it is desired to avoid.
The aim of the present invention is to provide a water-in-oil emulsion which has good stability, while at the same time retaining good cosmetic properties. In particular, it is desired to have available a stable water-in-oil emulsion which does not transfer after it has been used, in particular on the skin.
It has now been discovered, surprisingly and unexpectedly, that by using a specific emulsifying system, it is possible to obtain W/O emulsions which are not only stable over time, but are also stable with respect to variations in temperature, and which also show excellent cosmetic properties, as well as good resistance to transfer.
A subject of the present invention is thus a water-in-oil emulsion, comprising an aqueous phase and a fatty phase comprising a silicone oil, characterized in that it comprises an emulsifying system comprising at least one xcex1,xcfx89-substituted oxyalkylenated silicone of formula (I): 
in which: R=xe2x80x94(CH2)pOxe2x80x94(C2H4O)x(C3H6O)yR1 
where: R1 represents H, CH3 or CH2CH3,
p is an integer ranging from 1 to 5, x ranges from 1 to 100 and y ranges from 1 to 50,
it being possible for the units (C2H4O) and (C3H6O) to be distributed randomly or in blocks,
the R2 radicals represent a C1-C3 alkyl radical or a phenyl radical,
5xe2x89xa6mxe2x89xa6300,
and a co-surfactant chosen from the family of glycol mono- and/or diesters and glyceryl mono-, di- and/or triesters, and mixtures thereof.
For the purposes of the invention, the term xe2x80x9cco-surfactantxe2x80x9d refers to an amphiphilic compound, i.e. a compound comprising both a lipophilic part (apolar part) and a hydrophilic part (polar part) and which can be adsorbed onto a surface or an interface.
Another subject of the invention relates to a composition, in particular a cosmetic, dermatological, pharmaceutical or hygiene composition, comprising an emulsion as defined above.
The invention also relates to a non-therapeutic treatment process for the skin and/or keratin fibres, in particular a make-up process, which comprises applying an emulsion and/or a composition as defined above to the skin and/or to the keratin fibres.
Another subject of the invention relates to the use of an emulsifying system as defined above, for preventing, limiting and/or reducing the transfer and/or migration of a cosmetic, dermatological, hygiene and/or pharmaceutical composition, in particular a make-up and/or care composition for the skin, mucous membranes or semi-mucous membranes.
Another subject of the invention relates to a process for limiting, reducing and/or preventing the transfer of a cosmetic, dermatological, hygiene and/or pharmaceutical composition, in particular a make-up and/or care composition for the skin, mucous membranes, semi-mucous membranes and/or keratin fibres, this process comprises introducing an emulsifying system as described above into the said composition.
The W/O emulsion according to the invention fully satisfies the stability standards, i.e.:
resistance to the centrifugation test at 4000 rpm for 1 hour,
resistance to aging for 2 months at room temperature (25xc2x0 C.) as well as at 45xc2x0 C.,
resistance to 8 successive cycles of 8 hours each, where the temperatures of each cycle range from xe2x88x9220xc2x0 C. to +20xc2x0 C.
The emulsion according to the invention satisfies the following criteria:
it has and retains over the course of these tests a uniform and stable macroscopic and microscopic appearance (finely dispersed globules, absence of release) and
its viscosity is constant over time.
The emulsion according to the invention also has very good resistance to transfer. Furthermore, the emulsion applied to the skin has the advantage of not migrating or diffusing in the folds of the skin in particular on the eyelids and/or the wrinkles on the face, in particular on the lips and on the eyes, and the contours of these areas (crow""s feet).
It has been found that the emulsion used according to the invention applies and spreads easily and homogeneously, without leaving a greasy sensation, and has good cosmetic properties. The film obtained also has a light texture and remains comfortable to wear throughout the day.
Moreover, it is possible to add other adjuvants to the emulsion according to the invention, such as oils and/or powders (pigments and/or fillers), while at the same time retaining a stable emulsion. The emulsion is thus compatible with a large number of cosmetic adjuvants.
The emulsion according to the invention moreover has good sensory qualities, in particular great ease of application, comfort, softness, a good matte effect and good coverage, uniformity and staying power.
The emulsions of the invention comprise an emulsifying system comprising a specific xcex1,xcfx89-substituted oxyalkylenated silicone.
Throughout the text hereinabove and hereinbelow, the term xe2x80x9csiliconexe2x80x9d is intended to denote, in accordance with general acceptance, any organosilicon polymers or oligomers of linear or cyclic, branched or crosslinked structure, of variable molecular weight, obtained by polymerization and/or polycondensation of suitably functionalized silanes, and comprising a repetition of main units in which the silicon atoms are connected together via oxygen atoms (siloxane bondxe2x89xa1Sixe2x80x94Oxe2x80x94Sixe2x89xa1), optionally substituted hydrocarbon-based radicals being linked directly via a carbon atom onto the said silicon atoms. The hydrocarbon-based radicals which are most common are alkyl radicals, especially C1-C10 alkyl radicals and in particular methyl, fluoroalkyl radicals, aryl radicals and in particular phenyl. They can be substituted, for example, with C1-C40 ester or ether groups or C7-C60 aralkyl groups.
Thus, the xcex1,xcfx89-substituted oxyalkylene silicone which may be used according to the invention is an organosilicon polymer as defined above, of linear structure, substituted at the two ends of the main chain with oxyalkylene groups connected to the Si atoms via a hydrocarbon-based group.
The xcex1,xcfx89-substituted oxyalkylenated silicone which can be used according to the invention corresponds to the general formula (I) below: 
in which: R=xe2x80x94(CH2)pOxe2x80x94(C2H4O)x(C3H6O)yR1 
where: R1 represents H, CH3 or CH2CH3,
p is an integer ranging from 1 to 5, x ranges from 1 to 100 and y ranges from 1 to 50,
it being possible for the units (C2H4O) and (C3H6O) to be distributed randomly or in blocks,
the R2 radicals represent a C1-C3 alkyl radical or a phenyl radical, and
5xe2x89xa6mxe2x89xa6300.
Preferably, the xcex1,xcfx89-substituted oxyalkylenated silicone used according to the present invention corresponds to the general formula (I) for which all of the R2 radicals are methyl radicals and:
p ranges from 2 to 4,
x ranges from 3 to 100,
m ranges from 50 to 200.
Preferably also, the average molecular weight of R ranges from 800 to 2600.
Preferably, the weight ratio of the C2H4O units relative to the C3H6O units ranges from 100:10 to 20:80.
Preferably, this ratio is about 42/58.
Preferably also, R1 is a methyl group.
Even more preferably, the emulsion according to the invention comprises the xcex1,xcfx89 oxyalkylenated silicone of the following formula: 
in which:
m=100,
R=(CH2)3xe2x80x94Oxe2x80x94(C2H4O)xxe2x80x94(C3H6O)yxe2x80x94CH3, where x ranges from 3 to 100 and y ranges from 1 to 50, the weight ratio of C2H4O units to C3H6O units being about 42/58, the average molecular weight of R ranging from 800 to 1000.
The xcex1,xcfx89-substituted oxyalkylenated silicone as defined above is used according to the invention in a proportion ranging from 0.1 to 30%, preferably from 0.5 to 10%, by weight relative to the total weight of the emulsion.
Among the commercial products which can contain all or some of the xcex1,xcfx89-substituted oxyalkylenated silicones which may be used according to the invention as emulsifier are those sold under the names xe2x80x9cAbil EM 97xe2x80x9d by the company Goldschmidt or xe2x80x9cKF 6009xe2x80x9d, xe2x80x9cX22-4350xe2x80x9d, xe2x80x9cX22-4349xe2x80x9d or xe2x80x9cKF 6008xe2x80x9d by the company Shin Etsu.
The emulsifying system in the emulsions according to the invention also comprises a co-surfactant chosen from glycol mono- and/or diesters and glyceryl mono-, di- and/or triesters, and/or mixtures thereof.
Preferably, the co-surfactant has a HLB (Hydrophilic-Lipophilic Balance) of 7 or less.
Preferably, this co-surfactant is chosen from fatty acid esters of glycol and/or of glycerol such as glyceryl stearate, acetylated ethylene glycol stearate and isostearyl diglyceryl succinate.
Co-surfactants of this type are, for example the product sold by the company Hxc3xcls under the name xe2x80x9cImwitor 780Kxe2x80x9d, which is an isostearyl diglyceryl succinate.
Mention may also be made of the product sold under the name xe2x80x9cUnitwixxe2x80x9d by the company United Guardian, which is a product comprising a mixture of fatty acid esters of glycerol and of glycol in a ratio of between 75/25 and 95/5% by weight, the said fatty acids being C16-C36, at least 50% of the said fatty acids being Cl8-C22. 
Preferably, the co-surfactant is present in the emulsions and the compositions according to the invention in a proportion ranging from 0.05% to 10%, more preferably in a proportion ranging from 0.2% to 5%.
The fatty phase of the emulsions according to the invention comprises at least one volatile or non-volatile silicone oil.
The silicone oil which may be used according to the invention may be a linear, optionally functionalized or cyclic polydiorganosiloxane or an optionally crosslinked organopolysiloxane, or a mixture thereof.
The optionally functionalized linear polydiorganosiloxanes which may be used according to the invention correspond to the following general formula: 
in which:
X is xe2x80x94CH3 or OH and
n is an integer ranging from 0 to 2000.
Among these, mention will be made in particular of the products sold under the name xe2x80x9cAKxe2x80x9d by the company Wacker, xe2x80x9cSFxe2x80x9d by the company General Electric and xe2x80x9cAbilxe2x80x9d by the company Goldschmidt, such as the product xe2x80x9cAbil 10xe2x80x9d.
As cyclic polydiorganosiloxanes according to the invention, it is possible to use, alone or as a mixture, cyclomethicones of formula: 
in which:
n is an integer from 3 to 8.
Among the cyclomethicones which are particularly preferred, mention will be made of cyclotetradimethylsiloxane (n=4), cyclopentadimethylsiloxane (n=5) and cyclohexadimethylsiloxane (n=6).
It is possible in particular to use the products sold under the names xe2x80x9cDC Fluid 244xe2x80x9d, xe2x80x9cDC Fluid 245xe2x80x9d, xe2x80x9cDC Fluid 344xe2x80x9d and xe2x80x9cDC Fluid 345xe2x80x9d by the company Dow Corning.
Other cyclomethicones which may be used according to the invention are those sold under the names xe2x80x9cAbil K4xe2x80x9d by the company Goldschmidt; xe2x80x9cSilbione 70045 V2xe2x80x9d and xe2x80x9cSilbione Oil 70045 V5xe2x80x9d by the company Rhone-Poulenc; as well as xe2x80x9cVolatile Silicone 7158xe2x80x9d and xe2x80x9cVolatile Silicone 7207xe2x80x9d by the company Union Carbide.
Preferably, volatile silicone oils, including cyclomethicones, are used.
As indicated above, the silicone oil used according to the invention is preferably present in a proportion of at least 5%, and preferably ranging from 25 to 45%, by weight relative to the total weight of the emulsion.
The compositions of the invention may also comprise other silicone compounds.
Among these silicone compounds are poly(C1-C20)alkylsiloxanes, including phenylsilicone oils, as well as silicone gums and silicone waxes.
The silicone gums which may be used in the composition of the invention may be polysiloxanes with a high molecular mass, from about 200,000 to about 1,000,000, and with a dynamic viscosity of greater than 500,000 mPaxc2x7s. They may be used alone or as a mixture with a solvent such as a polydimethylsiloxane or polyphenylsiloxane oil, or a cyclomethicone.
The gums may be present in an amount up to 5% by weight of active material in the final composition, preferably up to 1%.
The silicone waxes which may be used in the composition according to the invention may be substituted linear polysiloxanes, for example, polyether silicone waxes and alkyldimethicones or alkoxydimethicones containing from 16 to 45 carbon atoms. These silicone waxes may be present in a proportion ranging from 0 to 15% by weight in the final composition, preferably in a proportion ranging from 2 to 10%.
The emulsions according to the invention may also comprise silicone resins comprising a combination of the units R3SiO1/2, R2SiO2/2, RSiO3/2 and SiO4/2.
The compositions according to the invention may also comprise non-silicone fatty substances, including pasty fatty substances, gums and waxes of plant, mineral, animal or synthetic origin.
The pasty fatty compounds may be defined with the aid of at least one of the following physicochemical properties:
having a viscosity ranging from 0.1 to 40 Paxc2x7s (1 to 400 poises), measured at 40xc2x0 C. with a Contraves TV rotary viscometer fitted with an MS-r3 or MS-r4 rotor at a frequency of 60 Hz, or
having a melting point ranging from 25 to 70xc2x0 C., preferably from 25 to 55xc2x0 C.
Preferred non-silicone waxes which may be used in the invention are waxes of animal origin, such as lanolin, beeswax, spermaceti, lanolin derivatives such as lanolin alcohols and hydrogenated, hydroxylated or acetylated lanolin, lanolin fatty acids and acetylated lanolin alcohol; waxes of plant origin, such as carnauba wax, candelilla wax, kapok wax, ouricury wax, rice wax, hydrogenated jojoba wax, alfalfa wax, Japan wax, cork fibre waxes or sugar cane wax, or even cocoa butter; mineral waxes, for example paraffin wax, montan wax, lignite wax, petrolatum wax, petroleum jelly wax or microcrystalline waxes, ceresin or ozokerite; synthetic waxes, such as polyethylene waxes, the waxes obtained by Fischer-Tropsch synthesis and linear esters resulting from the reaction of a saturated C10 to C40 carboxylic acid and a saturated C10 to C40 alcohol, such as myristyl myristate. Cetyl alcohol, stearyl alcohol, calcium lanolates or stearates, castor oil, palm oil, coconut oil, sunflower oil or hydrogenated coconut oil may also be used.
The fatty phase of the W/O emulsion according to the invention may comprise one or more hydrocarbon-based oil(s) in a proportion which can be up to 40% by weight relative to the total weight of the fatty phase of the emulsion.
A preferred hydrocarbon-based oil is any fluid oil (or mixture of oils) which is stable at the usual temperature at which the cosmetic, pharmaceutical or hygiene products are used, such as oils of plant, animal, mineral or synthetic origin, fluoro oils and triglycerides of C12-C18 fatty acids.
Preferred oils of plant or animal origin, which may be modified or unmodified are, for example, sweet almond oil, avocado oil, castor oil, olive oil, jojoba oil, sunflower oil, wheat germ oil, sesame oil, groundnut oil, grape seed oil, soybean oil, rapeseed oil, safflower oil, coconut oil, corn oil, hazelnut oil, karite butter, palm oil, (apricot) kernel oil or beauty-leaf oil.
Preferred oils of mineral origin are, for example, liquid paraffin.
Preferred synthetic oils are, in particular, volatile or non-volatile isoparaffins and polyisobutenes.
These fatty substances may be chosen in particular by a person skilled in the art so as to prepare a composition having the desired properties, for example in terms of consistency or texture. They are preferably used at a content of less than or equal to 7% by weight relative to the total weight of the emulsion, in order to preserve the advantageous properties of the emulsion used according to the invention.
Other liposoluble adjuvants which may be incorporated into the fatty phase are lipophilic UV screening agents, lipophilic vitamins, antioxidants, fragrances and ceramides.
The aqueous phase of the emulsion according to the invention may comprise water or a floral water such as cornflower water.
In addition, the aqueous phase may comprise from 0% to 14% by weight, relative to the total weight of the aqueous phase, of a lower C2-C6 monoalcohol and/or a polyol such as glycerol, butylene glycol, isoprene glycol or propylene glycol.
The aqueous phase may also contain adjuvants commonly used in cosmetic W/O emulsions, for example, lubricants, moisturizers such as glycerol and propylene glycol, trace elements, hydrophilic UV screening agents and polysaccharides, as well as electrolytes such as NaCl or MgSO4. The aqueous phase may also comprise active principles such as plant extracts, bacterial extracts, proteins or protein hydrolysates, and in particular hydrolysates of collagen or of elastin.
These active principles may be present in a proportion ranging from 1 to 15%.
Depending on the texture desired for the emulsion according to the invention, the proportion of the dispersed aqueous phase may range from 35% to 80%.
In general, the emulsion according to the invention may comprise from 30% to 55% by weight of fatty phase, from 5% to 12% by weight of surfactant, and from 35% to 75% by weight of aqueous phase.
In addition, the emulsion according to the invention may comprise one or more co-surfactants and one or more thickeners in concentrations preferably ranging from 0 to 6% by weight, relative to the total weight of the emulsion.
The thickener may be chosen from modified clays such as modified magnesium silicate (bentone gel VS38 from Rheox) or hectorite modified with distearyldimethylammonium chloride (bentone 38 CE from Rheox).
Advantageously, the emulsion according to the invention is substantially free of thickener.
The emulsion according to the invention may also comprise pearlescent agents, pigments and/or fillers usually used in cosmetic compositions.
The pigments may be present in the emulsion in a proportion ranging from 0 to 20% by weight, relative to the total weight of the emulsion, and preferably in a proportion ranging from 2 to 15%. They may be white or coloured, and inorganic and/or organic. Preferred inorganic pigments are titanium dioxide, zirconium dioxide or cerium dioxide, as well as zinc oxide, iron oxide or chromium oxide, ferric blue, pearlescent agents such as mica coated with titanium oxide, with iron oxide, with natural pigment or with bismuth oxychloride, as well as coloured titanium mica. Preferred organic pigments are, for example, carbon black, and barium, strontium, calcium and aluminium lakes. The pigments may also have a hydrophobic surface or may be treated so as to make their surface hydrophobic; this treatment may be carried out according to the methods known to those skilled in the art; in particular, the pigments may be coated with silicone compounds such as PDMSs and/or with polymers, in particular polyethylenes and/or amino acids.
Preferred coated pigments are, for example, the pigments sold under the name xe2x80x9cCovasilxe2x80x9d by the company Wacker (pigments containing triisostearyl titanate).
The pigments thus coated can be incorporated into the emulsion according to the invention in a proportion ranging from 0.1 to 15% by weight relative to the total weight of the emulsion.
The fillers, which may be present in the emulsion in a proportion ranging from 0 to 20% by weight relative to the total weight of the emulsion, preferably from 0 to 10%, may be mineral or synthetic, and lamellar or non-lamellar. Preferred fillers are, for example, talc, mica, silica, kaolin, Teflon, starch, natural mother-of-pearl, boron nitride, microspheres such as Expancel (Nobel Industrie), or microsponges such as Polytrap (Dow Corning). Preferably, spherical fillers which are less than 25 xcexcm in size are used, such as polyethylene powders, Nylon powders, microbeads of silicone resin (Tospearis from Toshiba) or silica microspheres, it being possible for these fillers to contribute towards improving the transfer-resistance properties of the emulsions of the invention.
In a preferred form of the invention, the emulsion comprises fillers having an average particle size equal to 15 microns or less. Preferably, these fillers are non spherical. Preferably, the weight ratio of the fillers to the oils, in the composition applied on the skin and after evaporation of the volatile oils, is from 30:70 to 50:50. More preferably, if n, represents the average refractive index of the totality of the fillers and if n2 represents the average refractive index of the totality of the oils, then:
0 less than |n1xe2x88x92n2|xe2x89xa60.3
and preferably,
0 less than |n1xe2x88x92n2|xe2x89xa60.15.
Thus, it is possible to obtain a foundation comprising very few pigments and still concealing the skin microreliefs. This composition shows soft-focus properties, in other words, it gives a blurred effect which conceals the skin microreliefs.
The emulsion according to the invention may also comprise a film-forming compound.
Thus the emulsion according to the invention may comprise polymers in aqueous dispersion, such as, for example, acrylic polymers, polyesters and/or polyurethanes in aqueous dispersion. For example, the emulsion may comprise a vinyl acetate/vinyl p-tert-butylbenzoate/crotonic acid copolymer as a stabilized, partially neutralized aqueous dispersion.
The emulsion according to the invention may also comprise a dispersion of polymer particles in a non-aqueous medium, as described, for example, in document EP 749,747.
The emulsion according to the invention may also comprise a cosmetically, pharmaceutically or hygienically acceptable medium. In this case, it may comprise any additive usually used in the field of cosmetics, pharmaceuticals or hygiene, such as antioxidants, dyes, fragrances, essential oils, preserving agents, cosmetic active agents, moisturizers, vitamins, sphingolipids, liposoluble polymers, in particular hydrocarbon-based polymers, such as polybutene, polyalkylenes, polyacrylates and silicone polymers which are compatible with the fatty substances.
These additives may be present in the composition in a proportion ranging from 0 to 10% by weight.
Needless to say, a person skilled in the art will take care to select optional complementary compounds, and/or the amount thereof, such that the advantageous properties of the composition according to the invention are not, or are not substantially, adversely affected by the addition envisaged.
The emulsions according to the invention may be in the form of a cosmetic product, and in particular in the form of a care product for the body and/or the face and/or the scalp, or alternatively a make-up product, in particular a foundation,a blusher, an eyeshadow, an eyeliner, a mascara or a lipstick.
They may also be in non-dyed form, optionally containing cosmetic active agents. The emulsion according to the invention may be in the form of a thickened emulsion, a fluid emulsion, a cream, a milk or a serum, which may be used as a care product or an antisun product.
Preferably, the emulsions according to the invention are in the form of a fluid.
The process for preparing the emulsions according to the invention comprised: (a) in a first stage, heating the fatty phase containing the emulsifying system up to a temperature which is sufficient to melt all of the constituents, preferably a temperature ranging from 60 to 85xc2x0 C., and then incorporating the optional additional liposoluble adjuvants, and (b) in a second stage, after cooling the fatty phase to a temperature ranging from 40 to 60xc2x0 C., adding the aqueous phase, brought to the same temperature, to the fatty phase with slow gentle stirring, and then, when the temperature has returned to about 25xc2x0 C., subjecting the preparation to vigorous stirring.
This second step may also be carried out by addition of the aqueous phase to the fatty phase with vigorous stirring, the aqueous phase being brought to the same temperature as the fatty phase.